Those undergarments in character creation have nothing to do with Zandalor's trunks, those are just cosmetic variants.
The real trunks are an actual unique item you have to equip in-game.
...which at this point appear to do nothing.
The trunks work, they just comment on things from time to time. You have to be wearing them for it to happen. Actually, you can have a companion wear them and they'll still comment (but less frequently as the comments are triggered by specific actions the wearer performs).
